Based on the demonstration of increased PIVKA-II levels, about 97% of all HD patients exhibit insufficient carboxylation activity. Together with the increased VC they represent an ideal population for interventional trials in the vitamin K system. Recently we were able to demonstrate that supplementation of vitamin K1 in such patients is well tolerated, shows only very few side effects and induces a dose dependent decrease of the inactive form Dephosphorylated noncarboxylated matrix Gla protein (dpucMGP) in serum over a six weeks period. In this trial we also observed that all dialysis patients included had insufficient vitamin K serum levels, indicating no substantial influence of food intake on vitamin K deficiency. In addition, this demonstrates that all patients have insufficient vitamin K levels to facilitate adequate MGP carboxylation.